1. Field of the Invention
The present invention relates to apparatus and method for inspecting breakdown of a conducting wire, and more particularly, to apparatus and method for determining if there is any defective wire among a plurality of wires arranged in parallel with each other and detecting an open location of the defective wire.
2. Description of the Related Art
In recent years, a technology of a flat panel display has been quickly advanced. Such a flat panel display is provided with a matrix grid. To form the matrix grid, a wire patterning process is essentially performed. A defect incurred during the wire patterning process affects on the yield of the display devices. Particularly, as the screen size of the display is increased, the open defect of the wires defining the matrix grid may be further increased, greatly affecting on the yield of the display devices.
Therefore, non-destructive testing has been performed for such a display or a printed circuit board (PCB). The non-destructive testing is performed to detect the defect by forming AC electric field around a metal object and measuring local variation of the electric field, the local variation being incurred by an eddy current induced to a boundary surface of the metal. Magnetic resistance, a coil, flux gate, and the like may be used as a sensor for detecting the variation of the electric field. Particularly, when a squid that is a superconducting quantum interference device is used, it becomes possible to detect a fine defect or a defect incurred on a location remote from a surface.
The above-described prior non-conductive testing using the eddy current is designed to demodulate a signal detected by a magnetic sensor by performing a two-dimensional scanning process and measure intensity of the modulated signal.
When an AC electric field having uniform amplitude is applied, a part of the electric field is shielded by the eddy current induced to the metal surface or a boundary surface of the metal, as a result of which the amplitude of the electric field is reduced. Therefore, by detecting the reduced amount of the amplitude, an eddy current shape corresponding to the actual shape of the metal is obtained. At this point, when there is a defect in the metal object, a local eddy current shape is obtained. This local eddy current shape has been analyzed using an electric field detecting sensor, a coil generating a uniform or local AC electric field, a signal generator and a lock-in amplifier measuring an rms or a peak-to-peak value from a signal of the sensor or other peak detectors.
Therefore, it becomes possible to detect a short circuit location between electrodes by detecting an abnormal signal generated at a breakdown portion without physically affecting on the test object. Such a non-destructive testing method using the magnetic sensor is well known in the art.
However, an open circuit test is conducted by flowing an AC current or by measuring a signal transmission failure caused by a capacitive coupling.
Since a panel has capacitive components itself to define an RC network, signal attenuation is growing more and more serious, the frequency property may be varied according to a model.
Particularly, when the signal transmission is measured by the capacitive coupling, a desired signal is obtained only when the wires are well aligned. The cost for making the measuring apparatus is increased due to the mechanical restriction conditions.
In addition to the above-described methods, the open test may be conducted using a magnetic detecting method using an electro-optic sensor. Although this method may be usefully applied to a variety of fields, it takes relatively long time to approach the surface of the test object.
Particularly, when the test object is large-sized, since the approach should be repeatedly performed, the total testing time is remarkably increased.